Cloud computing offers a lot of advantages, but it has some disadvantages as well. Some of the most creative uses of cloud computing use a hybrid of cloud servers and conventional servers to provide the best of both worlds. But there are disadvantages to such an approach, so here’s how engineering organizations have designed hybrid architectures to counter issues.
Cloud Computing Disadvantage 1: Slow Disk
On a cloud server, disk access speeds are dramatically slower than on a conventional server. This is because a server in the cloud uses virtualization so there is an additional layer of software between your code and the hard disk. Since fast disk is the key to running a big database server, this makes it really hard to run a big web app entirely in the cloud.
Hybrid Hosting Counter-Move: Combine your cloud and conventional servers in the same data center. Most servers (like web servers and application servers) don’t need to access fast disk. Where having slow disks really hurts you is the database. So you can host your application and web servers on cloud servers, and have them talk to a physical database server that’s in the same facility. Major League Gaming, a gaming site that hosts a social network for video gamers and hosts professional gaming competitions on-site, used this approach. Their database is hosted on a server at Rackspace that has a serious disk array (15 parallel 15k rpm SAS drives in a RAID-10 configuration). Application servers running on the Rackspace cloud connect to the database server.
“Having cloud servers that are hosted in the same data center as our dedicated servers gives us a lot of architectural flexibility” said Brian Corrigan, CTO of Major League Gaming. “Cloud servers have terrible I/O, so they don’t make sense for our database. But they’re great for app servers. Whenever we have a live competition, we spin up hundreds of app servers, and we shut them down as soon as the competition is over. This way we get the best of both worlds”.
CXT Software, a SaaS company that helps organizations track and manage shipping and delivery, uses a similar architecture on the SoftLayer cloud hosting platform. Its IT team originally set up its entire infrastructure on cloud servers at SoftLayer. “We encountered I/O bottlenecks too frequently, so we ended up converting our database servers to physical servers to handle the back end load.” said Shaun Richardson, VP of Services from CXT Software.
Cloud Computing Disadvantage 2: Paying By the Hour Is Expensive!
Paying by the hour may be more expensive for servers that need to be run 24-7, when compared to leasing hardware by the month.
Hybrid Hosting Counter-Move: If you’re using cloud computing for batch processing tasks, there’s nothing stopping you from running some dedicated servers that work off the same queue as your cloud computers. The way to do this is to calculate the minimum number of machines you need to run 24/7, and have those be physical servers. This way, you can use cloud computers as “peaker plants” for the situations when you need temporary extra capacity. Since you can order cloud servers automatically in response to increases in workload, this is a very economically efficient solution, and it’s the one my company (SlideShare) has used. This technique works really well for any job where the computers don’t need to have fast network connections with each other. Any kind of asynchronous job (like turning PowerPoint files into Flash, or transcoding videos) will qualify for this strategy.
Cloud Computing Disadvantage 3: The Largest Vendor Doesn’t Have a Hybrid Offering
The interesting thing about hybrid computing is that Amazon doesn’t provide it. In a cloud computing market thoroughly dominated by Amazon, hybrid computing allows conventional hosting companies like SoftLayer and Rackspace to offer something different and arguably superior. The move to servers powered by Flash SSD drives will increase the performance advantage of hybrid solutions over the next year, since you’ll be able to rent even faster disks on a physical server, while cloud disk performance will probably remain at the same speed! Will Amazon start offering “bare-metal” servers to counteract the competitive thread of hybrid computing?
Jonathan Boutelle is co-Founder and CTO of Slideshare, a web site for presentations that relies heavily on cloud computing. Previously, Jonathan was a principal at Uzanto, (a UI consulting firm) and worked as a software engineer at CommerceOne (a B2B enterprise software firm) and Advanced Visual Systems (a 3D graphics startup) You can find his presentations on cloud computing at slideshare.net/jboutelle, and his Twitter is @jboutelle. He also blogs at www.jonathanboutelle.com.
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